So this car has been out of commission for longer than I would like to admit. A few years ago when I drove it as my daily driver, my brake light fuse began to blow. It would blow as soon as I replaced the fuse. Ive replaced the turn signal switch (not much fun) and it still happens as soon as I replace the fuse. So I'm looking at what else it may be. When I crawled up under the dash again this last time I saw a white wire not attached on one end, looking like it had been ripped out. Can you guys please help me figure out what this goes to? I recently moved and my AIM is still in storage 😞 it doesn't appear do to be the white wire from the new turn signal switch, on either end.

 

First off, the wire is disconnected, so it can't be shorted and causing you fuse to blow. Tape it up and put it on your to do list.

A fuse that blows is pretty much a sign that the wiring is pinched, stripped or is somehow shorted to ground (the frame).

Get a bunch of fuses, better yet get a circuit breaker that fits in the fuse holder. Start off by removing the brake light lenses and inspecting the bulbs, are they the correct bulbs? Remove them and see if the fuse still blows. If they do, go under your Vet and inspect the wiring from the bulb sockets to where the wiring goes into the cab.

If it still blows, remove the drivers side threshold and pull back the carpet and inspect for damaged wiring...all the time tracing the specific wires that power the brake lights. If still ok, follow the wiring to the stop lamp switch and you WILL your short.

PM me if you still need help.

Michael

 

Good to know! I'm definitely more mechanically inclined than electrically.

I'll do just that, and report back with my findings. I'm really, really hoping it's something simple, but it usually never is!

That circuit breaker idea is fantastic, I've just been buying packages of fuses while troubleshooting.

Thanks for the help!

 

Since the fuse blows straight away (I assume this meas when you install the new fuse rather than as soon as you press the brake pedal) the the problem has to be around the dash somewhere. I'm wondering if that white wire should be connected to the brake switch and has come out leaving a short there.

The other thing to try is removing the hazard flasher and seeing if that changes anything.

 

So I pulled all the tail lights and rechecked the fuse, and it still blows as soon as I place the fuse to the fuse box. I checked the wiring at the tail lights and it all looks alright. One of the sockets was replaced, but it looks like the wiring is pretty secure and protected.

As for the white wire, there is one attached to the brake switch. It comes out of the switch, runs with another wire (orange? I forget, even though I just looked at it) into a larger bundle. The white wire on both sides of the turn signal switch connector are installed and secure, leaving that white one hanging. I don't know where that one goes.

I just bought a short tester to help me find the short. It's really hard because the fuse instantly blows.

I really appreciate your guys' help! I'm definitely learning wiring basics as I go.

 

Two other things on that fuse, one is the hazzard lights, pulling the flasher should eliminate that. The other is the key buzzer, it is in the first pic, the black box by the fuse box with the orange and green wires going into it, unplug that connector and see if it still blows the fuse. If it still blows with those removed, try unplugging the harmonica connector to the signal switch. Process of elimination.

 

Okay! I found something

When the brake light switch at the base of the steering column is unplugged, the fuse does not blow. The bad news is that I don't know what to do from here! I originally replaced the turn signal switch because of this issue, and while I am not saying it couldn't be the switch, it is new, and has already been replaced. Both connectors look fine. All the wires are secured, there's no burnt or melted areas, etc. How do I go about tracing the short at this point? I really appreciate the help fellas. I can R&R a motor no problem. But this stuff always baffles me.

 

Ok, you've determined it's in the brake light circuit and not the hazards. Next unplug the harmonica connector going to the signal switch and extract the green and the yellow wires on the car side of the plug, these are the wires going to the left and right signalbrake lights. Then plug that connector back together minus the green and yellow and plug the brake light switch back in and see if the short is still there or gone.

 

So I'm stumped. I managed to get the green and yellow wires off of the steering column side, but for the life of me I can't figure out how to remove the wires on the black/dash harness side. When I removed them from the steering column/white side, and plugged the two connectors back together, the fuse didn't pop. I don't know if that tells me the switch is bad, or if the dash harness has a short in it somewhere. I don't have a hazard flasher relay installed in the fuse box, could that have anything to do with it? I doubt it, but figured I would bring it up anyway.

 

You do not have to worry about removing the green and yellow wire from the other connector.

NOW...knowing that the fuse does NOT blow when these wires are not connected. Take one wire...the color is up to you. And with connector under the column still connected. Take the color wire and then go in on the backside of the black connector and touch the terminal to the terminal that is still caged in the black connector and see if the fuse blows. TEST both wires.

What this will do is tell you which side of the rear taillights you have a problem.....OR...you could still have a problem in the rear wiring going to your taillights where you can disconnect the rear wiring harness from the dash harness over there by your fuse panel.

DUB

 

You didn't say when you unplugged the hazard flasher, so plug it back in now to see if it's a problem.

 

If the fuse no longer blows immediately with the brake light switch unplugged then that's what I would test next. Use a test light to check between 12v and both pins on the switch (with the connector unplugged) It shouldn't light up at all. Or if you only have an ohm meter then check between the switch and ground, it should be open.

 

More progress! I'm about 95% there I believe. At this point the brakes work, the running lights work and the turn signals work. My only problem is that when I hit the brakes the left side is at High Brightness and the right side is at Low Brightness (dual filament bulbs). Also, when my headlights are on (meaning running lights are on) the right turn signal doesn't work. Under all other conditions, everything works (brakes + turn, turn only, running lights only, etc)

Here's a video showing what I'm talking about, in case that's as hard to follow for you as it was for me to write.

https://drive.google.com/open?id=0B8...zRYYVcxbU1nSEU

 

I had a very similar problem on my 81, and I am an electrician.
No guarantee its the same thing, but I replaced the right turn signal socket, and it was fixed. After checking the harness and the grounds, it was all that was left.

 

Seems like maybe the wires are crossed for the right side or maybe the bulb is in wrong. The reason the signal doesn't work with the tail lights on is just that it's dim and you can't see it flashing.

 

I'll try reversing the bulb, but I dont know if that's possible because of the little indexing pins on the bulb housing. If not that I'll replace the socket. I'm so close!

 

Brake switch is shorted to Ground.
Use an ohm-meter to verify.

 

It is not your brake light switch being shorted to ground because one sided works correctly.

READ THIS!!!!!

If I read what you wrote CORRECTLY.

If your brake lights work PERFECTLY.....AND....your turn signals work PERFECTLY...when you DO NOT----repeat---DO NOT have the headlight/running lights on. THEN....

When you turn you headlights/running lights your problems BEGIN. Your problems is a GROUND issue in the rear of the car on the side that is NOT acting correctly. This is a FACT.

I seriously DOUBT it is an improperly installed light bulb due to IF your lights work perfectly WITHOUT the headlights/running lights on...then that is NOT the problem.

Knowing that the rear light bulbs have two filaments in them...BUT...they BOTH share the SAME common ground....which is the socket. SO....if the socket is NOT grounded...then the lights are working due to it finding a ground using the filament that is NOT being used. BUT..once you need both filaments to work...there is NO GROUND for it to work....thus...a dim light.

A simple test is to get a wire and ground it and KNOW that it is a good ground wire. Pull your sockets out of your taillight housing on the side that is not working correctly. TURN ON your headlights....then turn on your ignition...and then turn on the turn signal for the side that is not working and THEN...take the wire you grounded and strip it so you have copper strands that you can go down BESIDE the glass bulb and contact the socket. It should work correctly when you do it.....THUS...is telling you that you need to get that black wire that plugs into your socket be a good ground again.

The plug that is in the side of your taillight socket are known to go bad. Sometimes by simply wiggling it and pushing it in will get the bulb to work. BUT...that is only going to work IF the wire is actually grounded and not break somewhere else.

DUB

 

Confirming a good ground as Dub described.

 

So if I was 95% there before, now I'm back at 0%.

I went out today to see if I could figure out the headlight + right turn signal issue. The ground on that side was not very secure, so I soldered it together and used some heat shrink to fix it.

I went to go test it out, and my fuse was blown. Instant dread. I replaced it, and it instantly blew again. I don't know what to do at this point. I swapped the turn signal and the hazard flasher relays to verify that it was good, and they both work as intended (when in the turn signal relay spot). It seemed like putting in the hazard relay was what fixed it last time. I really just want to drive this car. It has a brand new engine with less than 10 miles on it. Brand new carb with zero miles. Starts up instantly, sounds great, idles perfectly, but I can't drive it because of this brake light issue.

I unplugged the turn signal switch and it didn't blow again. So that's verified.

I removed the green & yellow wires from the turn signal switch, reconnect both sides of the turn signal connector, and it blows again, which is a different result than before. I'm to the point of giving up! It's so frustrating. It doesn't help that I don't fully understand electrical circuits, which just makes the entire situation more confusing to me.

I pulled all of the bulbs in the tail lights, had the turn signal switch fully connected (green & yellow wires in) and the fuse blows. I had a spare brake light switch, so I plugged it in, and it still blows.

I just don't know what to do. I'm about to just take it to a shop, as much as I hate to do that.